Welcome to my guide, hope you have as much fun as i have playing Pantheon.
Pantheon is one of the first champions i bought and i loved him from the start, he is a great damage dealer and isn't squishy at all.

Pantheon has massive damage early game, he can domine the lane easily and doesn't have many hard counters. He is an off tank assassin and can take a lot of damage while going for the opponent AD Carry during teamfights. He also has an almost global ultimate that can be a game changer if used correctly.

Pros

* Strong early/mid game
* Doesn't have many counters
* Almost global ultimate
* THE POKING GOD
* Has a decent stun
* Highest base movement speed in the game
* Amazing Tower Diver

Cons

* Mana hungry early game
* Needs a good early game to be strong late
* No natural sustain

Laning with Pantheon is a breeze, just keep last hitting while zoning your opponent with Spear Shot. When the enemy is low, go in with Spear Shot, Aegis of Zeonia, Heartseeker Strike, then Spear Shot again and Ignite.
So the combo goes: Q W E Q

When the enemy escapes with low HP, don't be afraid of ulting to finish him off, even if close to the tower. Don't forget you're an awesome tower diver!

Pantheon needs a good early game to be effective late, but this isn't a problem, you should have dominated the lane and maybe get fed, so the job is even easier now. Keep split pushing with Heartseeker Attack, don't worry if your team is rushing a lane, you have your Grand Skyfall in case of a teamfight. Help warding the map when it's possible.

During teamfights, try always to ult above all the enemy team, especially close to their AD Carry. Just use your full combo on him and he's gone. Don't forget that Heartseeker Strike will be causing a lot damage after building your AD items, so try to hit as many enemies as possible.